Process for the production of single- or multi-phase materials o

Details Process for the production of single- or multi-phase materials o Process for the production of single- or multi-phase materials o

1995-04-26

1997-05-20

Azpuru, Carlos A.

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Implant or insert

523115, 623 16, A61E 202, A61F 228

Patent

active

056310161

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/FR93/01064 filed Oct. 28, 1993.
The present invention relates to a process for the production of single- or multi-phase materials of biological interest such as composites or ceramics particularly from bioactive mineral powders such as calcium phosphate powders, as well as products for biological use obtained by practice of the process.
Mineral powders take part nowadays in the composition of a large number of products. The essential problem always resides in the interconnection of the constituents of said powders. Thus, ceramics constituted by compacted mineral powders are obtained only under the action of either high temperature and/or very high pressure, thereby giving rise to a deterioration of the structures.
Concomitantly, dynamic compaction is a process nowadays widely used as a process for bonding or connection of metallic powders. Such a process is for example described in the article of D. G. MORRIS "Bonding processes during the dynamic compaction of metallic powders", Mater. Sci. & Eng. Vol. 157, pp 187 to 195. Similarly, in the patent DE-A-2.138.388 is described a process for dynamic compaction which is applicable to compacting essentially metallic powders. The patent FR-A-2.396.613 describes a process for compacting powder by means of a shockwave generated by launching a projectile which directly strikes the matrix within the cavity of the specimens containing the powder. This patent is applicable to powders which are metallic or not, without supplemental precision.
Finally, the patent DE-A-3.706.821 discloses a process for compacting by explosion for the production of refractory ceramic members. However, in the case of all these patents, no particular application of the obtained powders is disclosed.
The principle of dynamic compaction is simple and consists in generating a shockwave also called an elastic compression wave which strikes the specimen disposed in a matrix so as to deform it while giving rise to partial fusion of the grains at their surface and hence an interconnection of the grains.
The inventors of the present invention have discovered that, in a surprising manner, it is possible to obtain with bioactive and hence biocompatible materials such as bioactive mineral powders, the same result and thus to obtain in solid form blocks of material which had never been able to be compacted with techniques currently used such as sintering. In addition to the possibility of obtaining new materials, the drawbacks connected with sintering are also avoided, which required compressing the material at high temperature so as to give rise to a fusion of the constituents, then an agglomeration of the microcrystals which form upon cooling, these latter remaining thus interconnected at the grain boundaries. This temperature elevation modifies the crystallographic properties and hence generally the biological activity of the material. Moreover, with certain mineral powders such as calcium phosphate powders, there are obtained calcium phosphate ceramics which are very fragile because the thermal exchanges in particular during the step of cooling of the sintering process give rise to stresses which tend to crack the final product.
The object of the present invention is therefore to be able to provide, particularly from bioactive mineral powders, ceramics, indeed composites, by association with metallic or non-metallic matrices, without temperature elevation and with the possibilities of controlling the size and shape of the final crystals as well as the homogeneity of the mixture obtained, while maintaining optimum biological activity of the composition.
Another object of the present invention is to be able to associate organic substances, particularly the active principles, without degradation of these latter, with these mineral powders to obtain a progressive diffusion of said principle within the organism.
Finally, a last object of the invention is to obtain new ceramics based particularly on calcium salts in particular calcium phosphates never before produced.
The

REFERENCES:
patent: 4218255 (1980-08-01), Bajpai et al.

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